How can I create a Spline chart with WPF without using a Windows Forms Control or aftermarket package?

Question

I have a need to create a spline chart natively in WPF via either Dynamic Data Display or using the WPF DataVisualization toolkit. Does anyone know if it's possible?
If so, can you point me to an example of a Spline chart?

Thanks in advance.

Answer 1

您是否尝试过PolyBezierSegment

Answer 2

Sounds like you are looking for a best fit curve to draw in WPF. You would have to create a custom control to draw it, but a Bezier spline should work nicely for you if you can do the drawing. Here is a class I wrote that will allow you to generate a set of smooth points from a small set of seed points. Instantiate the object, set the SeedPoints property to a set of points, then call the GenerateSpline(int NumberPointsToGenerate) to get the points for a smooth curve. I generally use about 40 points to generate a really smooth curve.

/// <summary>
/// Class to generate a Bezier Curve from a set of seed points.  
/// Note that this is a best fit curve through a set of points 
/// and a Bezier does NOT require the curve to pass through the points.
/// </summary>
public class BezierSpline
{
    /// <summary>
    /// Default Constructor
    /// </summary>
    public BezierSpline()
    {
        SeedPoints = new List<PointF>();
    }

    /// <summary>
    /// Constructs a BezierSpline object using SeedPoints
    /// </summary>
    /// <param name="seedPoints"></param>
    public BezierSpline(IList<PointF> seedPoints)
        : this()
    {
        SeedPoints = new List<PointF>(seedPoints);
    }

    /// <summary>
    /// Set of SeedPoints to run the spline through
    /// </summary>
    public List<PointF> SeedPoints { get; set; }

    /// <summary>
    /// Generates a smooth curve through a series of points
    /// </summary>
    /// <param name="numberPointsToGenerate">Number of points to generate between P0 and Pn</param>
    /// <returns>IList of Points along the curve</returns>
    public IList<PointF> GenerateSpline(int numberPointsToGenerate)
    {
        List<double> ps = new List<double>();
        List<PointF> np = new List<PointF>();
        for (int i = 0; i < SeedPoints.Count; i++)
        {
            ps.Add(SeedPoints[i].X);
            ps.Add(SeedPoints[i].Y);
        }

        double[] newpts = Bezier2D(ps.ToArray(), numberPointsToGenerate);
        for (int i = 0; i < newpts.Length; i += 2)
            np.Add(new PointF(newpts[i], newpts[i + 1], 0));

        return np;
    }

    private double[] Bezier2D(double[] b, int cpts)
      {
          double[] p = new double[cpts * 2];
          int npts = (b.Length) / 2;
          int icount, jcount;
          double step, t;

          // Calculate points on curve
          icount = 0;
          t = 0;
          step = (double)1 / (cpts - 1);

          for (int i1 = 0; i1 < cpts; i1++)
          { 
              if ((1.0 - t) < 5e-6) 
                  t = 1.0;

              jcount = 0;
              p[icount] = 0.0;
              p[icount + 1] = 0.0;
              for (int i = 0; i != npts; i++)
              {
                  double basis = Bernstein(npts - 1, i, t);
                  p[icount] += basis * b[jcount];
                  p[icount + 1] += basis * b[jcount + 1];
                  jcount += 2;
              }

              icount += 2;
              t += step;
          }
          return p;
      }

    private double Ni(int n, int i)
    {
        return Factorial(n) / (Factorial(i) * Factorial(n - i));
    }

    /// <summary>
    /// Bernstein basis formula
    /// </summary>
    /// <param name="n">n</param>
    /// <param name="i">i</param>
    /// <param name="t">t</param>
    /// <returns>Bernstein basis</returns>
    private double Bernstein(int n, int i, double t)
       {
           double basis;
           double ti; /* t^i */
           double tni; /* (1 - t)^i */

           if (t == 0.0 && i == 0) 
               ti = 1.0; 
           else 
               ti = System.Math.Pow(t, i);

           if (n == i && t == 1.0) 
               tni = 1.0; 
           else 
               tni = System.Math.Pow((1 - t), (n - i));

           //Bernstein basis
           basis = Ni(n, i) * ti * tni; 
           return basis;
       }

    /// <summary>
    /// Gets a single y value for a given x value
    /// </summary>
    /// <param name="x">X value</param>
    /// <returns>Y value at the given location</returns>
    public PointF GetPointAlongSpline(double x)
    {
        return new PointF();
    }

    public static int Factorial(int n)
    {
        int f = 1;

        for (int i = n; i > 1; i--)
            f *= i;
        return f;
    }
}